drivers/soc/aspeed/aspeed-lpc-snoop.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright 2017 Google Inc
   4  *
   5  * Provides a simple driver to control the ASPEED LPC snoop interface which
   6  * allows the BMC to listen on and save the data written by
   7  * the host to an arbitrary LPC I/O port.
   8  *
   9  * Typically used by the BMC to "watch" host boot progress via port
  10  * 0x80 writes made by the BIOS during the boot process.
  11  */
  12
  13 #include <linux/bitops.h>
  14 #include <linux/clk.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/fs.h>
  17 #include <linux/kfifo.h>
  18 #include <linux/mfd/syscon.h>
  19 #include <linux/miscdevice.h>
  20 #include <linux/module.h>
  21 #include <linux/of.h>
  22 #include <linux/of_device.h>
  23 #include <linux/platform_device.h>
  24 #include <linux/poll.h>
  25 #include <linux/regmap.h>
  26
  27 #define DEVICE_NAME     "aspeed-lpc-snoop"
  28
  29 #define NUM_SNOOP_CHANNELS 2
  30 #define SNOOP_FIFO_SIZE 2048
  31
  32 #define HICR5   0x80
  33 #define HICR5_EN_SNP0W          BIT(0)
  34 #define HICR5_ENINT_SNP0W       BIT(1)
  35 #define HICR5_EN_SNP1W          BIT(2)
  36 #define HICR5_ENINT_SNP1W       BIT(3)
  37 #define HICR6   0x84
  38 #define HICR6_STR_SNP0W         BIT(0)
  39 #define HICR6_STR_SNP1W         BIT(1)
  40 #define SNPWADR 0x90
  41 #define SNPWADR_CH0_MASK        GENMASK(15, 0)
  42 #define SNPWADR_CH0_SHIFT       0
  43 #define SNPWADR_CH1_MASK        GENMASK(31, 16)
  44 #define SNPWADR_CH1_SHIFT       16
  45 #define SNPWDR  0x94
  46 #define SNPWDR_CH0_MASK         GENMASK(7, 0)
  47 #define SNPWDR_CH0_SHIFT        0
  48 #define SNPWDR_CH1_MASK         GENMASK(15, 8)
  49 #define SNPWDR_CH1_SHIFT        8
  50 #define HICRB   0x100
  51 #define HICRB_ENSNP0D           BIT(14)
  52 #define HICRB_ENSNP1D           BIT(15)
  53
  54 struct aspeed_lpc_snoop_model_data {
  55         /* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
  56          * can use them.
  57          */
  58         unsigned int has_hicrb_ensnp;
  59 };
  60
  61 struct aspeed_lpc_snoop_channel {
  62         struct kfifo            fifo;
  63         wait_queue_head_t       wq;
  64         struct miscdevice       miscdev;
  65 };
  66
  67 struct aspeed_lpc_snoop {
  68         struct regmap           *regmap;
  69         int                     irq;
  70         struct clk              *clk;
  71         struct aspeed_lpc_snoop_channel chan[NUM_SNOOP_CHANNELS];
  72 };
  73
  74 static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
  75 {
  76         return container_of(file->private_data,
  77                             struct aspeed_lpc_snoop_channel,
  78                             miscdev);
  79 }
  80
  81 static ssize_t snoop_file_read(struct file *file, char __user *buffer,
  82                                 size_t count, loff_t *ppos)
  83 {
  84         struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
  85         unsigned int copied;
  86         int ret = 0;
  87
  88         if (kfifo_is_empty(&chan->fifo)) {
  89                 if (file->f_flags & O_NONBLOCK)
  90                         return -EAGAIN;
  91                 ret = wait_event_interruptible(chan->wq,
  92                                 !kfifo_is_empty(&chan->fifo));
  93                 if (ret == -ERESTARTSYS)
  94                         return -EINTR;
  95         }
  96         ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
  97         if (ret)
  98                 return ret;
  99
 100         return copied;
 101 }
 102
 103 static __poll_t snoop_file_poll(struct file *file,
 104                                     struct poll_table_struct *pt)
 105 {
 106         struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
 107
 108         poll_wait(file, &chan->wq, pt);
 109         return !kfifo_is_empty(&chan->fifo) ? EPOLLIN : 0;
 110 }
 111
 112 static const struct file_operations snoop_fops = {
 113         .owner  = THIS_MODULE,
 114         .read   = snoop_file_read,
 115         .poll   = snoop_file_poll,
 116         .llseek = noop_llseek,
 117 };
 118
 119 /* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
 120 static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
 121 {
 122         if (!kfifo_initialized(&chan->fifo))
 123                 return;
 124         if (kfifo_is_full(&chan->fifo))
 125                 kfifo_skip(&chan->fifo);
 126         kfifo_put(&chan->fifo, val);
 127         wake_up_interruptible(&chan->wq);
 128 }
 129
 130 static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
 131 {
 132         struct aspeed_lpc_snoop *lpc_snoop = arg;
 133         u32 reg, data;
 134
 135         if (regmap_read(lpc_snoop->regmap, HICR6, &reg))
 136                 return IRQ_NONE;
 137
 138         /* Check if one of the snoop channels is interrupting */
 139         reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
 140         if (!reg)
 141                 return IRQ_NONE;
 142
 143         /* Ack pending IRQs */
 144         regmap_write(lpc_snoop->regmap, HICR6, reg);
 145
 146         /* Read and save most recent snoop'ed data byte to FIFO */
 147         regmap_read(lpc_snoop->regmap, SNPWDR, &data);
 148
 149         if (reg & HICR6_STR_SNP0W) {
 150                 u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
 151
 152                 put_fifo_with_discard(&lpc_snoop->chan[0], val);
 153         }
 154         if (reg & HICR6_STR_SNP1W) {
 155                 u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
 156
 157                 put_fifo_with_discard(&lpc_snoop->chan[1], val);
 158         }
 159
 160         return IRQ_HANDLED;
 161 }
 162
 163 static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
 164                                        struct platform_device *pdev)
 165 {
 166         struct device *dev = &pdev->dev;
 167         int rc;
 168
 169         lpc_snoop->irq = platform_get_irq(pdev, 0);
 170         if (!lpc_snoop->irq)
 171                 return -ENODEV;
 172
 173         rc = devm_request_irq(dev, lpc_snoop->irq,
 174                               aspeed_lpc_snoop_irq, IRQF_SHARED,
 175                               DEVICE_NAME, lpc_snoop);
 176         if (rc < 0) {
 177                 dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
 178                 lpc_snoop->irq = 0;
 179                 return rc;
 180         }
 181
 182         return 0;
 183 }
 184
 185 static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 186                                    struct device *dev,
 187                                    int channel, u16 lpc_port)
 188 {
 189         int rc = 0;
 190         u32 hicr5_en, snpwadr_mask, snpwadr_shift, hicrb_en;
 191         const struct aspeed_lpc_snoop_model_data *model_data =
 192                 of_device_get_match_data(dev);
 193
 194         init_waitqueue_head(&lpc_snoop->chan[channel].wq);
 195         /* Create FIFO datastructure */
 196         rc = kfifo_alloc(&lpc_snoop->chan[channel].fifo,
 197                          SNOOP_FIFO_SIZE, GFP_KERNEL);
 198         if (rc)
 199                 return rc;
 200
 201         lpc_snoop->chan[channel].miscdev.minor = MISC_DYNAMIC_MINOR;
 202         lpc_snoop->chan[channel].miscdev.name =
 203                 devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, channel);
 204         lpc_snoop->chan[channel].miscdev.fops = &snoop_fops;
 205         lpc_snoop->chan[channel].miscdev.parent = dev;
 206         rc = misc_register(&lpc_snoop->chan[channel].miscdev);
 207         if (rc)
 208                 return rc;
 209
 210         /* Enable LPC snoop channel at requested port */
 211         switch (channel) {
 212         case 0:
 213                 hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W;
 214                 snpwadr_mask = SNPWADR_CH0_MASK;
 215                 snpwadr_shift = SNPWADR_CH0_SHIFT;
 216                 hicrb_en = HICRB_ENSNP0D;
 217                 break;
 218         case 1:
 219                 hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W;
 220                 snpwadr_mask = SNPWADR_CH1_MASK;
 221                 snpwadr_shift = SNPWADR_CH1_SHIFT;
 222                 hicrb_en = HICRB_ENSNP1D;
 223                 break;
 224         default:
 225                 return -EINVAL;
 226         }
 227
 228         regmap_update_bits(lpc_snoop->regmap, HICR5, hicr5_en, hicr5_en);
 229         regmap_update_bits(lpc_snoop->regmap, SNPWADR, snpwadr_mask,
 230                            lpc_port << snpwadr_shift);
 231         if (model_data->has_hicrb_ensnp)
 232                 regmap_update_bits(lpc_snoop->regmap, HICRB,
 233                                 hicrb_en, hicrb_en);
 234
 235         return rc;
 236 }
 237
 238 static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
 239                                      int channel)
 240 {
 241         switch (channel) {
 242         case 0:
 243                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 244                                    HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
 245                                    0);
 246                 break;
 247         case 1:
 248                 regmap_update_bits(lpc_snoop->regmap, HICR5,
 249                                    HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
 250                                    0);
 251                 break;
 252         default:
 253                 return;
 254         }
 255
 256         kfifo_free(&lpc_snoop->chan[channel].fifo);
 257         misc_deregister(&lpc_snoop->chan[channel].miscdev);
 258 }
 259
 260 static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
 261 {
 262         struct aspeed_lpc_snoop *lpc_snoop;
 263         struct device *dev;
 264         struct device_node *np;
 265         u32 port;
 266         int rc;
 267
 268         dev = &pdev->dev;
 269
 270         lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
 271         if (!lpc_snoop)
 272                 return -ENOMEM;
 273
 274         np = pdev->dev.parent->of_node;
 275         if (!of_device_is_compatible(np, "aspeed,ast2400-lpc-v2") &&
 276             !of_device_is_compatible(np, "aspeed,ast2500-lpc-v2") &&
 277             !of_device_is_compatible(np, "aspeed,ast2600-lpc-v2")) {
 278                 dev_err(dev, "unsupported LPC device binding\n");
 279                 return -ENODEV;
 280         }
 281
 282         lpc_snoop->regmap = syscon_node_to_regmap(np);
 283         if (IS_ERR(lpc_snoop->regmap)) {
 284                 dev_err(dev, "Couldn't get regmap\n");
 285                 return -ENODEV;
 286         }
 287
 288         dev_set_drvdata(&pdev->dev, lpc_snoop);
 289
 290         rc = of_property_read_u32_index(dev->of_node, "snoop-ports", 0, &port);
 291         if (rc) {
 292                 dev_err(dev, "no snoop ports configured\n");
 293                 return -ENODEV;
 294         }
 295
 296         lpc_snoop->clk = devm_clk_get(dev, NULL);
 297         if (IS_ERR(lpc_snoop->clk)) {
 298                 rc = PTR_ERR(lpc_snoop->clk);
 299                 if (rc != -EPROBE_DEFER)
 300                         dev_err(dev, "couldn't get clock\n");
 301                 return rc;
 302         }
 303         rc = clk_prepare_enable(lpc_snoop->clk);
 304         if (rc) {
 305                 dev_err(dev, "couldn't enable clock\n");
 306                 return rc;
 307         }
 308
 309         rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
 310         if (rc)
 311                 goto err;
 312
 313         rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
 314         if (rc)
 315                 goto err;
 316
 317         /* Configuration of 2nd snoop channel port is optional */
 318         if (of_property_read_u32_index(dev->of_node, "snoop-ports",
 319                                        1, &port) == 0) {
 320                 rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
 321                 if (rc) {
 322                         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 323                         goto err;
 324                 }
 325         }
 326
 327         return 0;
 328
 329 err:
 330         clk_disable_unprepare(lpc_snoop->clk);
 331
 332         return rc;
 333 }
 334
 335 static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
 336 {
 337         struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
 338
 339         /* Disable both snoop channels */
 340         aspeed_lpc_disable_snoop(lpc_snoop, 0);
 341         aspeed_lpc_disable_snoop(lpc_snoop, 1);
 342
 343         clk_disable_unprepare(lpc_snoop->clk);
 344
 345         return 0;
 346 }
 347
 348 static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
 349         .has_hicrb_ensnp = 0,
 350 };
 351
 352 static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
 353         .has_hicrb_ensnp = 1,
 354 };
 355
 356 static const struct of_device_id aspeed_lpc_snoop_match[] = {
 357         { .compatible = "aspeed,ast2400-lpc-snoop",
 358           .data = &ast2400_model_data },
 359         { .compatible = "aspeed,ast2500-lpc-snoop",
 360           .data = &ast2500_model_data },
 361         { .compatible = "aspeed,ast2600-lpc-snoop",
 362           .data = &ast2500_model_data },
 363         { },
 364 };
 365
 366 static struct platform_driver aspeed_lpc_snoop_driver = {
 367         .driver = {
 368                 .name           = DEVICE_NAME,
 369                 .of_match_table = aspeed_lpc_snoop_match,
 370         },
 371         .probe = aspeed_lpc_snoop_probe,
 372         .remove = aspeed_lpc_snoop_remove,
 373 };
 374
 375 module_platform_driver(aspeed_lpc_snoop_driver);
 376
 377 MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
 378 MODULE_LICENSE("GPL");
 379 MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
 380 MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");